Sun deprivation could cause a seasonal peak in babies born with schizophrenia

Some cases of schizophrenia may be caused by mothers being deprived of sunshine during pregnancy, an expert has suggested.

It has been known for more than 80 years that there was a seasonal peak of cases in North America and Europe in March.

Babies born between February and April are 10% more likely to develop schizophrenia than those born at other times of the year.

It has been suggested that mothers who had had an infection, such as flu, during the pregnancy at the time the babies' brains were being formed were more likely to have "schizophrenic babies".

Anyone looking for a single 'Big Bang' theory for the development of schizophrenia is likely to be disappointed

Gary Hogman,National Schizophrenia Fellowship

But Dr John McGrath, a psychiatrist at the Queensland Centre of Schizophrenia Research in Brisbane, Australia, suggests it could be the lack of UV light that is the key factor.

The National Schizophrenia Fellowship told BBC News Online the theory was interesting - but that pregnant women who did not get much sun should not be "blamed" if their child developed the disease.

Causes

Around 250,000 in Britain have schizophrenia.

There is no one cause for schizophrenia.

Various genes and environmental factors could be involved, but scientists have not yet pinned down exactly how.

But reporting Dr McGrath's research, the New Scientist says that season of birth accounts for more cases of schizophrenia than any other known risk factor - including genetic causes.

Only a city birth is a higher risk factor than being born in the spring.

Dr McGrath found that in Queensland, there is a peak in the birth of schizophrenic babies every three to four years.

This does not coincide with the big flu outbreaks, but does happen with the same frequency that the El Nino weather system gives the area extremely gloomy weather and therefore a lack of UV light.

The Southern hemisphere gets around 15% more UV light than the northern, which the scientists say would explain the European and American peaks.

Vitamin link

One of the things UV does is convert a cholesterol-like molecule in the skin to vitamin D.

Dr McGrath said: "Vitamin D is low in winter, low in cities and low in dark-skinned migrants to northern climates".

Those are all high risk factors for schizophrenic births.

However, it is not known what role vitamin D might play in the development of the brain, though experiments suggest it may be needed in building the brain and developing tissue.

Tests on rats, carried out by Dr McGrath earlier this year, found pregnant rats deprived of UV light or vitamin D had offspring with enlarged ventricles, as seen in the brains of schizophrenics.

But he warned pregnant women should not take vitamin D supplements because too much can cause birth defects.

'No single theory'

Experts say both the UV light/vitamin D theory and respiratory infections during pregnancy may explain a proportion of schizophrenia cases.

Gary Hogman, head of policy and campaigns for the National Schizophrenia Fellowship, said: "Anyone looking for a single 'Big Bang' theory for the development of schizophrenia is likely to be disappointed.

"Schizophrenia remains poorly understood, but is almost certainly an umbrella term covering a range of conditions with a number of common symptoms."

He said both genes and environmental factors were likely to be involved.

"Any research that seeks to shed light on these complex interactions is to be welcomed, but the results should not be presented as the definitive cause of schizophrenia.

"Nor should they seek to 'blame' mothers for 'causing' schizophrenia in their unborn children."